James Hill for The New York Times

Grigory A. Melkonyants, the deputy director of Golos, Russia's only independent election monitoring organization, said he was worried that the group’s 3,000 monitors would be excluded from polling stations.

The organization, Golos, has already posted reports of more than 4,500 violations of election law in the prelude to the voting on Sunday. Golos receives financing from Western governments, including the United States, and some Russian officials have suggested that the organization’s real aim is to incite an Arab Spring-type revolution inRussia.

Pressure on Golos, an 11-year-old group whose name means “vote” in Russian, began mounting last Sunday, when Mr. Putin attacked “so-called grant recipients” that he said were interfering with elections on behalf of foreign governments. “Judas,” he said, “is not the most respected biblical figure among our people.”

The accusations became specific this week, when lawmakers from three parties appealed to the federal prosecutor to investigate Golos. Blistering attacks appeared in several pro-government news outlets. In one article, a leader of Mr. Putin’s party, United Russia, likened Golos to a group announcing that “we got money from Al Qaeda, and now we want to see how elections in Tatarstan are going.”

The mood at Golos’s Moscow office was jumpy on Thursday. Grigory A. Melkonyants, the organization’s deputy director, said he was worried that the group’s 3,000 monitors would be excluded from polling stations, and that they might even be in danger, after Mr. Putin’s use of the word “Judas.” He said it was possible that Golos would be shut down by the authorities before Sunday.

“We cannot predict what will happen tomorrow, or what will happen in an hour,” Mr. Melkonyants said. “This is already an open war that they have declared on us, and the overwhelming weight is on their side.”

A letter delivered by prosecutors on Thursday said that one of Golos’s most popular features — an online “map of violations” where people can post reports — violates a Russian law against publishing data, especially polling results, during the five days before voting. This is an administrative violation punishable by a fine of up to 100,000 rubles, or about $3,200.

The letter also accuses Golos, which has been preparing for Sunday’s election for years, of “dissemination of rumors under the guise of trustworthy reports, with the goal of defaming a party as well as its individual members.”

Though United Russia, which now has a commanding majority in Parliament, faces no powerful competitors in the election, opinion polls suggest that it will lose 50 to 60 seats, reflecting growing weariness with leadership that has not changed in a decade. State officials at all levels have been told to guard against significant losses.

Meanwhile, amateur observers are pushing back, using the Internet to expose violations that include offers of cash and threats to cut off financing. Dmitri Merezhko, Golos’s communications director, said that events this fall — including the collapse of a pro-business party, Right Cause, and Mr. Putin’s announcement that he will run for president again, after a stint as prime minister and two previous terms as president — “ignited something in the most active part of the public.”

“Maybe someone thinks we are the reason,” Mr. Merezhko said, referring to Golos. “But we are not the reason.”

Golos’s critics in the Russian government say its work is tainted by the money it receives from two American agencies, the National Endowment for Democracy and the United States Agency for International Development. A promotional video clip for a report scheduled to be broadcast on Friday on the NTV channel, owned by the Russian energy giant Gazprom, features images of suitcases stuffed with $100 bills juxtaposed with footage of Golos’s leaders as a portentous voice asks, “Who is behind these ‘independent observers?’ ” A pro-government blogger has posted what appears to be paperwork showing that Golos received $92,653 from the United States government for the month of February.

Russian officials have invoked the memory of the 2004 Orange Revolution in Ukraine, which many people here believe was propelled by American agents. Maksim Rokhmistrov, one of the three lawmakers who signed the appeal to the prosecutor, said he was worried that Golos’s reporting could provoke civil unrest.

“A girl dances with the guy who takes her to dinner, as they say,” Vzglyad, a daily newspaper, quoted Mr. Rokhmistrov as saying this week. “The question of maintaining stability in the state worries everyone at election time. No one here wants to see the beginning of our own Egypt, or our own Libya.”

Mr. Melkonyants has given a number of interviews with the news media since the critiques began to appear, arguing that the foreign financing does not compromise Golos’s objectivity or violate any Russian law. He told the radio station Ekho Moskvy that much of Golos’s money came from European donors like the Helsinki Committee and the European Commission.

He said Golos had submitted to rigorous audits by Russian tax authorities and the Ministry of Justice, and had repeatedly tried to secure financing from the Russian government but had been refused.

Mr. Melkonyants is scheduled to appear in a Moscow courtroom on Friday at the request of prosecutors.

Though every election monitoring mission has come under pressure from government officials, “it has never been so high in my memory,” he said, adding that he could not blame Golos’s partners for keeping their distance now. “There is no need to say that they are cowards,” he said. “Believe me, all of us — including the political parties — we’re all in a situation that is not simple, not simple at all.”